As refractories for steel casting, into which molten steel at about 1500.degree. C. is poured, there has been used a graphite containing refractory composition of high thermal shock resistance. The refractory composition has a high thermal conductivity because of the contained graphite, and it allows a large amount of heat dissipation from the outer surface thereof. The graphite containing refractory composition is pre-heated before being used to prevent the generation of cracks due to abrupt thermal change; however, these prevention abilities are limited because the temperature is rapidly dropped for a period of time from the completion of heating to the beginning of casting.
To cope with the above problem, for example, Japanese Unexamined Utility Model Publications Nos. SHO 55-43616 and SHO 60-34354 disclose a method of attaching Al.sub.2 O.sub.3 --SiO.sub.2 or Al.sub.2 O.sub.3 --SiO.sub.2 --CaO based ceramic heat-insulating fibers on the surfaces of refractories. This method, however, is disadvantageous in that while the contained fibers provide high heat resistance and heat-insulation, the fibers, which have sizes in the order of several microns and are harmful to the human body, are set loose in the atmosphere when the heat causes loss of the binder.
As a means for obtaining a general heat-insulating structure in place of the above ceramic heat-insulating fibers, a monolithic refractory material mixed with organic fibers lost by heating may be proposed. However, to obtain a good heat-insulating effect with only organic fibers, a large amount of the organic fibers must be added, which has the disadvantage of significantly reducing the strength of the refractory material.
The subject to be solved by the present invention is to provide a heat-insulating refractory material, which does not contain environmentally and hygienically problematic ceramic heat-insulating fibers, only contains organic fibers to the extent necessary to improve adhesive rate upon spraying, and can nevertheless achieve a specified heat-insulating effect.